a. Field of the Invention
The invention generally relates to antibodies that bind two or more thromboxane A2 metabolites, and more particularly to antibodies that bind common epitopes in two or more target thromboxane B2 metabolites derived from thromboxane A2 and to the uses for these prepared antibodies.
b. Background
Aspirin (acetyl salicylic acid) has been in use in the United States for at least 100 years, with approximately 80 million aspirin tablets being consumed in America each day (self medicated or physician prescribed). Beyond pain relief, aspirin has been shown to reduce risk of cerebrovascular ischemia, myocardial infarction, angina, and recurrent blockage of arteries (collectively referred to as thrombotic disease (Antithrombotic Trialists' Collaboration, BMJ, 324:71-86, 2002)). Thrombotic disease is one of the world's leading causes of morbidity and mortality, and its prevalence is increasing (Lopez et al., Nat. Med., 4:1241-1243, 1998).
The Food and Drug Administration has recently recommended that persons suffering from thrombotic disease take from between 50 mg aspirin/day to 325 mg aspirin/day. However, higher doses of aspirin pose health risks in certain segments of the population, including stomach irritation, ringing in ears, allergic reactions and in children, Reye's syndrome.
Aspirin has been shown to inactivate cyclooxygenase (also known as COX or prostaglandin G/H synthase), a membrane bound enzyme responsible for the oxidation of arachidonic acid to prostaglandin G2 (Awtry et al., Circulation, 101:1206-1218, 2000). This reaction is a precursor to the formation of a variety of prostanoids, including thromboxane A2 (TxA2), a potent platelet aggregator, and metabolites of thromboxane A2 such as thromboxane B2. In general, aspirin has been shown to reduce COX activity (there are actually two COX enzymes termed COX-I and COX-II) and thereby reduce the levels of downstream prostanoid development. Inactivation of these pathways ultimately limits thrombotic events by suppressing at least the ability of platelets to aggregate (Hamberg et al., PNAS, 72:2994-2998, 1975; Ellis et al., Science, 193:1135-1137, 1976).
Although the mechanism of aspirin inhibition of COX-1 is understood, recent studies suggest that not all users respond to aspirin to the same degree. A lack of response to aspirin in a user is generally referred to as “aspirin resistance.” Person's suffering from aspirin resistance typically show either a lack of biochemical changes while on aspirin, i.e., user shows no or little reduction in TxA2 (and TxB2), platelet activation and/or aggregation, or the user may experience an ischemic event while on aspirin (Bhatt et al., Nature Rev., 2:15-28, 2003; Hankey et al., Lancet, 367:606-617). In either case, the prevalence of aspirin resistance in the population has been reported to be between 5 and 57% (Gum et al., Am J Cardiol, 88:230-235, 2001; Tarjan et al., Orv. Hetil, 140:2339-2343, 1999; Sane et al., Am J Cardiol, 90:893-895, 2002; Helgason et al., Stroke, 25:2331-2336, 1994). Identification of whether or not an individual is aspirin resistant prior to or during a thrombotic event would be extremely useful to a healthcare professional. An aspirin resistant individual would obviously receive an alternate dosage, drug or modified anticoagulant therapy.
Typically, studies using aspirin have focused on optimizing the amount of aspirin required for an individual to reduce the risk associated with thrombotic disease. Blood based assays have been developed that measure in vitro platelet aggregation as a measure of aspirin's effectiveness. However, these methods are not quantitative and can be affected by factors that are unrelated to aspirin sensitivity. In addition, a quantitative immunoassay is available for 11-dehydrothromboxane B2 (a TxA2 metabolite) detection in urine requiring the use of a polyclonal antibody to 11-dehydrothromboxane B2. The assay is helpful in that aspirin effectiveness can be determined from a subject's urine, but the polyclonal antibody does not provide highly reproducible or specific results.
U.S. Pat. No. 6,967,083 (herein '083) to Ens provides methods for identifying an optimal minimal aspirin dose for a patient that is specifically tailored to the patient's platelet response levels. The method utilizes a solid substrate coated by an agent capable of reacting with 11-dehydro thromboxane B2 in the urine, but provides little or no guidance as to how to reproducibly achieve this detection result given the tools described in the patent. For example, no agents in the '083 patent are described or shown that react with 11-dehydro thromboxane B2 or other thromboxane A2 metabolites.
As such, there is a need in the art to develop a highly specific and reproducible assay that measures effectiveness of aspirin in reducing platelet aggregation in a subject. The assay should be effective at measuring a dose of aspirin tailored to a particular subject for reducing thrombotic disease. In addition, there is a need in the art for a highly specific and reproducible assay that quickly identifies aspirin resistant individuals, thereby facilitating a health care professional's determination on a best course of treatment in the absence of aspirin.
Against this backdrop the present invention has been developed.